Me and some of my friends want to have "Battles' (In a sense) Over our local network, Like trying to get root in each others system and make his PC shutdown. Maybe setting up like different objectives, Like copying a file from each other or something. Is this possible over Local network, and if so, Where can we study some of this stuff? We want to study both Attacking and Defending against this stuff, So if you've got good info on both, That would be great, thanks.

When attacking your target, you are going to need to exploit a specific weakness. This can be in the form of insecure code, poor configuration, weak passwords, etc. If the target is not running a service (web, SSH, email, DNS, etc.) it is going to be significantly harder to attack.

For defense, a properly-configured firewall as a main defense and an anti-virus as a secondary should be sufficient for your case.

The Firewall is your first line of defence, since it will avoid possible attack vectors.IDS, IPS, and AV software is your second line of defence because if a file is modified or somone starts sending commands you would notice and would be able to take action.The third line is to simply know your computer better than an attacker. Try to bust in and do all evil stuff to it before letting anybody connect and attack it.

What? That's not true at all. There are tons of attacks that could give a fuck less if your traffic is encrypted or not. MITM using sslstrip or sslify to get around encryption. Viruses can spread over an SSL tunnel just as easily as they can over plain old HTTP. I can walk up to your computer and take the HD out. You might be running a vulnerable service or client. How is encrypting all your traffic making you 100% safe?